A largish ‘pot’ with no base - does such a thing exist?

Do you mean like a chimney pit or a piece f large drainpipe?

Have I got the vision right?

Try Mr Google - you can find anything using him. Or look on Amazon. You might need to be imaginative about possible names, but you certainly get forcing pots for encouraging plants to grow taller or earlier.

I think one kind of pot is called "Long Tom".

I'd look for a chimney pot or a large drainpipe, like Lathyrus3.

I have a fern planted in an old chimney pot in a place where the soil is very dry. It's a bit taller than you describe but successful.

Churchview

I have a fern planted in an old chimney pot in a place where the soil is very dry. It's a bit taller than you describe but successful.

I’ve done the same with an old chiminea chimney. I call it my fake tree fern.

When you can "straight sides" are you thinking of an actual pot or a planter to give you a raised bed

If the latter there are lots of options at places like B&Q
www.diy.com/search?term=planters+%26+raised+beds

I have some old clay drainage pipes that appeared when we dug deeply. I put them over plants that are in danger of being eaten by insects or mice. They are about 10 inches tall and 6 or 8 inches across, with both ends open. If you could find something like that, they would be excellent.

Try googling - I've just found these £6.50 each - watlingreclamation.co.uk/product/terracotta-land-drainage-pipes-reclaimed

Thanks everybody - I really want something wider than e.g. a drainage pipe. Maybe I’ll have to cut the base off an existing pot somehow.

www.google.com/url?q=https://elixirgardensupplies.co.uk/product/bottomless-plant-pots-ring-culture-tomato-planter/%3Fsrsltid%3DAfmBOoolfskWaFS_Gq9tHBFz8mfws6lRJlCKbnNP-mbR23iiv_Gno3Lw&sa=U&sqi=2&ved=2ahUKEwjxkPTQjt2NAxXTSvEDHUKAGXwQFnoECCYQAQ&usg=AOvVaw1wpL4dIDRrAnhbaht10C2_

This do?

How about a rhubarb forcing pot? They are open at the bottom and come in all shapes, some reclaimed of which can be rather expensive! Try Ebay or Etsy.

www.themiddlesizedgarden.co.uk/sloping-garden-solutions-real-truth-about-gardening-slope/

For a patch of planting above the slope, could you punch holes in some thing like an old baby bath, sink it up to almost the rim and plant in that? When you water that or when it rains, the water would stay in it and not run downhill.

Would something like this work?
www.indooroutdoors.co.uk/products/square-rustic-steel-raised-flower-bed-tree-planter?_gl=1*y6kboq*_up*MQ..&gclid=Cj0KCQiAvP-6BhDyARIsAJ3uv7YAd4M0-Vb5BTwXwmPjvLB8OnEi9rSyYkJrW0K_vFGbQTSJFQSme2kaAiAOEALw_wcB

I've used one myself and it works well.

What you can do is get a terracotta pot the appropriate size, and carefully knock the bottom out with a hammer before putting it in position and planting up. I've successfully used this technique, suggested by Bunny Guinness, lots of times in similar situations.

The gardener Bunny Guinness is a big fan of cutting the bottom off of all sizes, which enables plants to simply grow down and find the water. It can also help to create local points by raising up plants in beds etc around the garden. My husband has cut the bottom off of several pots for me, with a small handheld angle grinder. It’s noisy and dusty but really not difficult. There is always a slight risk that the pot will break, and I’d be reluctant to do this to a very expensive pot, but I would say have a go at doing this yourself or just ask around and find someone who has an angle grinder who might do it for you. It really only takes a few minutes.

Why do I never spot the mistakes until I post here? Will we ever get an edit button on Gransnet?
I should’ve said that Bonnie Guinness is a big fan of cutting the bottom off of POTS of all sizes……and these create FOCAL points around the garden.

For anyone wanting to make a real statement with something like this, you can also buy bottomless Corton steel circular planters in whatever size you want, made to order. But they are expensive.

Trawl a builder's supplier for wide drain pipe. They are tough black plastic so not pretty. I have sweetpeas growing in one. Unfortunately the weeds grow right up through!

www.cor-ten-steel.co.uk/index.php/corten-planters-round/?utm_content=cpl003t&utm_source=page&utm_medium=website

luxunique.co.uk/shop/bottomless-round-corten-steel-planter/
Or Google large bottomless planter or large clay drainage pipe.

Chimney pot or earthenware pipe

I bought a circular metal raised bed from Gardening Express - mine is 3ft diameter, and they do a 2ft diameter one too.